This invention relates generally to a miniature variable capacitor and more particularly to a miniature variable capacitor provided with a driving mechanism of a construction wherein a miniature variable capacitor main body is accommodated within a recess of a driving pulley. According to this construction, the variable capacitor is reduced its thickness dimension, thereby afford miniaturization and simplification. The miniature variable capacitor provided with a driving mechanism is appropriately applied, for instance, to a tuning apparatus in radio receiver. A rotor shaft of the variable capacitor structure is integrally formed with the driving pulley.
A miniature variable capacitor provided with a driving mechanism known heretofore has a general construction wherein a rotor shaft projects downwards from a base plate supporting thereon a variable capacitor main body consisting of stator plates and rotor plates, and a driving pulley fitted around the rotor shaft is secured thereto by a screw. When the driving pulley is rotated together with the rotor shaft for variably adjusting capacitance, a stop plate fitted to the rotor shaft comes to engagement with a pair of pins embeddedly fixed to the upper surface of the base plate, thus restricting a rotational movement of the rotor plates.
The conventional variable capacitor of the above described construction is, however, accompanied by difficulties in that the overall thickness of the driving pulley and the stop member is added to overall thickness dimension of the variable capacitor, thus causing the variable capacitor to be of a relatively larger size. In addition to this, a position where the stop plate engages with the pins is above the base plate and near the rotor shaft. This arrangement results in poor accuracy of the determination of the positions where the rotor plates stop.
Furthermore, since the driving pulley is secured to the rotor shaft by a screw, there are accompanied by difficulties in that the number of constituting elements required increases, that the number of processes required to production increases, and that looseness occurs between the driving pulley and the rotor shaft due to possible loosening of the screw, which rather lowers assembling accuracy and thereby deteriorates performances of the variable capacitor. A section of the driving pulley where the screw is screwed increases the thickness dimension of the variable capacitor.